Along with the development of people's consciousness of environment protection, water-based paint is becoming more and more popular. This is mainly because the water-base paint does not contain an organic solvent and so is beneficial to the atmosphere and indoor environment. Nevertheless, the base material adopted by the existing water-based paint is mainly conventional emulsion and water-soluble resin. The former contains a large amount of emulsifiers and the water-proof property of the coating is poor. The latter comprises the acrylic or alkyd resin having a high acid value of 60-90 as a base and the self-drying property of the coating is poor.
In order to solve the above-mentioned technical problems, many efforts have been made. For example, an anticorrosive primer made from a water-based polyurethane-modified alkyd resin is disclosed in a AT patent No. 8,302,121, which is prepared by reacting a carboxyl-containing and polyether segment-containing acrylic acid-modified alkyd resin (A) and a polyurethane-modified alkyd resin (B) with a diisocyanate in an organic solvent to obtain an acrylic acid-polyurethane-modified alkyd resin, removing the solvent by vacuum distillation, adding an organic amine to neutralize the carboxyl group, emulsifying with water to obtain an acrylic-polyurethane modified alkyd emulsion, which is then mixed with the pigment, filler and aids to obtain an anticorrosive primer, which can be used for anticorrosive coating steel members. Nevertheless, owing to the presence of the hydrophilic polyether segment in the molecular chain of the resin, the water-proofness of the coating is poor and thus the anticorrosive property of the coating is adversely affected.
A water-based acrylic acid anticorrosive paint (Showa High polymer Co.) is disclosed in a JP patent No. 03,192,166, which comprises as a base material an acrylic emulsion made by emulsion polymerizing the monomers including styrene, alkyl (meth)acrylate esters, and glycidyl acrylate esters. The anticorrosive paint is mainly used as a pre-coating primer and a protective primer in equipment maintenance. Owing to the corrosion accelerating effect of the ion SO42− produced by a persulfate initiator during emulsion polymerization, the problem of flash and back corrosion occurs. Meanwhile the coating film is more hydrophilic and the rust resistance poor.
A water-based epoxy polyester primer (Dai Nippon Ink Co.) is disclosed in a JP patent No. 05,306,377, which is prepared by reacting an epoxy resin with a drying oil fatty acid to produce a drying oil-modified epoxy ester resin, and then reacting the epoxy ester resin with a carboxy-containing ethylenic monomer and other ethylenic unsaturated monomers to produce a vinyl-modified epoxy resin, then removing the solvent by vacuum distillation, neutralizing the carboxy group by adding an amine, emulsifying with water to form an epoxy ester emulsion, and mixing the resultant emulsion with a pigment, a filler, and an aid to obtain the anticorrosive primer. Owing to a great quantity of organic solvents contained in the intermediate product acrylic acid-modified epoxy ester resin during the synthesis of the resin, a treatment for the removal of the solvent is necessary, which consumes a large amount of energy and thus makes the production efficiency decrease.
Therefore, an object of this invention is to provide a new acrylic acid-modified epoxy polyester resin, which can be prepared from a raw material available easily and has a low cost. The resin can be used to prepare a water-based epoxy polyester emulsion, thereby producing a cost-effective water-based paint with excellent rust resistance.
Another object of this invention is to provide a process for preparing said new acrylic acid-modified epoxy polyester resin. By adopting said process, said resin can be economically and easily obtained.
A further object of this invention is to provide an emulsion produced from said resin.
Still a further object of this invention is to provide a process for preparing said emulsion.
A further object of this invention is to provide a water-based paint comprising the emulsion according to this invention as the base material. Said water-based paint has excellent rust resistance and low production cost.